US2513992A - High altitude fuel system - Google Patents

Description

y 1950 L. G. BURNS 2,513,992

HIGH ALTITUDE FUEL SYSTEM Filed April 3, 1942 2 Sheets-Sheet 1 fizverzzgof" loads. 6 ficuvw J July 4, 1950 L. G. BURNS 2,513,992

HIGH ALTITUDE FUEL SYSTEM Filed April 3,.1942 2 Sheets-Sheet 2 Fuc/ )empera TEMP. "F

FUEL FLOW r6. R H.

Fuel pres sure .s/er assure l0 I5 a0 36 40 ALT/TUDE- rfi/omsnuo FEET.

6 Eli/677.507"

loads C;- .Burvza Patented July 4, 1950 HIGH ALTITUDE FUEL SYSTEM Louis G. Burns, Willoughby, Ohio, assignor, by

mcsne assignments, to; Borg-Warner Corporation, Chicago, 111., a corporation of Illinois Application April 3, 1942, Serial No. 437,478

6 Claims. (Cl. 103-413) This invention relates to liquid pumpingor transfer systems and methods for handling liquids which have a tendency to incorporate air therein and particularly to an arrangement for properly conditioning volatile fuel for transfer from the fuel tank to an aircraft engine. I

The problem of air bubble inclusion in the fuel pumping or transfer system has become increasingly serious with the extensive use of high octane highly volatile fuel and flight at extremely high altitudes where the surrounding atmospheric pressure is considerably reduced. Also the present standard aircraft fuel has a vapor pressure of six to seven pounds per square inch, at 100 F. which adds to the difficulty of control and handling.

Under the above circumstances it has been found very diflicult to prevent occluded air from becoming precipitated in the fuel in the carburetor metering passages, with the result that faulty metering occurs even before vapor-lock in its true sense is encountered.

I have found that this problem can be solved.

by properly conditioning the fuel in the tank at the point of delivery to the pumping equipment proper, and it is the object of this invention to teach how this proper conditioning of the fuel may be accomplished.

Another object of the invention is to provide a method of stabilizing volatile liquid fuel for high altitude performance and preventing Vapor lock in airplane fuel systems by providing a body or pond of volatile liquid fuel, as in a tank or otherenclosure, flowing the liquid fuel from the pond in a selected path under hydraulic head pressure, preferably from or near the bottom of the tank, locally agitating the liquid fuel about to flow from the pond to generate bubbles of gas and vapor from the liquid fuel to an extent substantially in excess of that resulting spontaneously from reduction of atmospheric pressure due to increase in altitude and to create in the pond a counterfiow of liquid fuel carrying the bubbles of gas and vapor laterally outward from the selected path, directing the counterflow away from the selected path and upwardly to the surface of the pond to release the bubbles of gas and vapor, causing the bubble-freed liquid fuel again to flow in the selected path, so as to eliminate from the fuel flowing from the pond occluded gas, and vapor, which normally would become separated therefrom upon further increase in altitude and cause the formation of bubbles in the fuel, and subjecting the flowing fuel immediately after agitation thereof to pres- 2 sure sufficient to prevent spontaneous separation of additional gas, andvapor',"therefrom, whereby to deliver from the pond stable, liquid fuel substantially free of bubbles. .1 It is a further object to disclose a preferred arrangement effective to remove or'eject the occluded air from the fuel introduced thereto from the fuel tank, returning the air to the tank and delivering the air-feed fuel to the fuel trans-- fer or pumping system for movement to the carburetor and aircraft'engine for consumption. Still another object is the disclosure of an arrangement of the above character which is also applicable to the conditioning and transfer of liquid generally where there exists the problem ofair inclusion or vapor-lock. A more specific object is the provision in corribination in an assembly of the present type of an optimum construction of propeller blade for conditioning the liquid and particularlyhighly volatile fuel brought into contact therewith. Another particular object is provision of an improved arrangement of the above type which incorporates the additional feature of super charging the fuel tank for preventing the loss of fuel during sustained flight.

Other and more particular objects, advantages and uses of my invention willbecorne apparent from a reading of the following specification taken in connection with. the ac companying drawings forming a part thereof and wherein: I 1

Fig. 1 is a schematic broken-away view ofan aircraft incorporating a preferred embodiment of my fuel conditioning and transfer arrangement; i Fig. 2 is an axial cross-sectional viewtaken substantially on the line 2-2 of Fig. .1, and showing to advantage the preferred arrangement of conditioning means located adjacent to and in communication with the fuel in the tank;

Fig. 3 is an axial cross-sectional view similar to Fig. 2 but showing the preferred arrangementof inlet separator for a horizontal installation; Fig. 4 is a plan view of my improved air foil or converging'tip propeller construction;

Fig. 4a is a cross-section view taken substantially on the line 4a.4a of Fig. 4; Fig. 5 is a view of a modified arrangement ha ing general application;

Fig. 6 is a perspective-like View showing the actual air separation at the inlet as obtained with the arrangement of Figs.-1, 2 and 4 simulating conditions of flight at 30,000 feet; w

Fig. '7 is a view similar to that of Fig. 6 but taken at 40,000 feet; and

Fig. 8 presents a set of curves which bring out to advantage the improved results obtained by conditioning the fuel or ejecting the vapor therefrom before introducing the same to the pumping or transfer arrangement proper, the 30,000 and 40,000 feet: points corresponding respectively to Figs. 6' and 7.

Referring in greater detail to the figures of the drawings, numeral it indicates schematically theessential portions of an aircraft having a preferred embodiment of my invention incorporated thereon and including an engine. H supplied with volatile fuel from a tank l2 carried in plane wing l3 at a position remote from and lower than the position of fuel introduction to the motor. I provide a special arrangement indicated generally at I5 for receiving the fuel from tank i2, eliminating or ejecting the occluded air therefrom and pumping the same tothe main fuel pump Hi located adjacent a'nd driven. from the aircraft enginev H, this main pump in turn delivering the fuel to carburetor H from which it is. fed to engine llv for'consumption.

arrangement Indicated at I5 includes essentia'lly an air or vapor ejector assembly designated. generally at 20' which receives fuel from tank l2: andis effective to eject the occluded air therefrom and to deliver air-freed fuel to a pump proper indicated generally at 21 which in turn raises! the pressure of the air-freed fuel and delivers the same to the: inlet of main engine driven fuel pump it. Thepump 25- is disclosed. as being of the centrifugal booster type including a centrifugal impeller-Zia, and it has been found that the same cooperates to particular novel advantage inthe present combination as will appear. It is to be understood, however, that in certain broader aspects of. my invention, the. same has application with other forms ofv pumping means.

Thus; twovery important things, are accomplished first, the air which is unavoidably incorporated in the volatile fuel entering the ejector is. removed and. returned to the body of fuel in the tank, this beingv accomplished by assembly 20,. and second, the pressure in the transfer line to the motor driven pump it is boosted andmain-tained at a value above the critical pressure, below which pump l6 would tend to. pull the volatile fuel apart and cause the condition known as vapor-lock.

Air or vapor ejector 20 preferably includes a propeller-like blade assembly 2 5 comprising a pair of oppositely radially extending blades 26, each blade having an air foil'or converging tip construction shown to particular advantage in Figs. 4 and 4a. A housing or throat ring 32 is formed with a generally converging or funnel.- like chamber 33 having a relatively large termi nal' orport' 34 and a restricted outlet terminal or port 35". Thesurrounding wall of chamber 33 is shown as generally concave or cup-like in shape, which has been found to give particularly good flow characteristics. The propeller assembly '25 preferably has an overall diameter slightly less than that of terminal port 34 and is positioned for coaxial rotation in substantially opposed relation to the terminal port 34. The propeller blade pitch and direction of rotation are suchvv as to move the liquid from the central portion of port 34 in. the direction of the restricted outlet 35',"which communicates with the vanes 2th of the centrifugal impeller Zia. The vane 25b extend from a generally central position, exposed to the flow from the restricted outlet port 35, radially outwardly in opposed spaced relation to the outwardly flared housing wall a surrounding the discharge port 35. The radially outer terminal of the vanes 2H2 discharge into chamber 2lc, shown as a conventional scroll or volute chamber of a centrifugal booster pump. It is considered important that the overall diameter of the propeller be substantially greater than the diameter of the restricted outlet port 35. It is important that the liquid moving capacity of propeller 25 be substantially in excess of the rate of flow through outlet port 35 so that an excess of liquid will be driven or circulated back from chamber 33 past the peripheries of the propeller blades 26 and into tank I2. It has been discovered that by properly proportioning this return circulation or excess of fuel ejected back past the propeller the same is effective to remove therewith the critical portion of the oceluded air which has entered chamber 33 past the: inner or central portion of the propeller.-

For improving; the air and liquid separation, a generally ring-like member is spaced from the propeller and includes: an inlet port l! connected by a generally convex inner wall 42 to a restricted outlet terminal orifice 43. This restricted terminal it-has a diameter lessv than the overall diameter of the propeller, thus facilitating the introduction. of liquid to the general central portion of the propeller, the ring 40 being further provided with a diverging underside wall portion 4.4L, serving in conjunction with the wall of port 34- to facilitate the ejection of vapor or air-laden excess fuel. A screen 56 may surround ring 40 and housing 32, while a similar screen ll may cover the port M in ring 49, thus preventing the entry of foreign particles.

Referring to Fig. there is shown an alternative: form of separator or ring-like member 400.. This form of separator is particularly adaptable for a horizontal installation and differs from separator 40 principally in that it is considerably longer and hasa straightfunnel-like sheet metal wall. Separator 40a may be supported from a perforatedv tube Ml-b. protruding from the sepa rator wall.

Without attemptingto fullyexplain the theory or' mode of operation which accounts for the improved results obtained, it would appear that a number of factors enter into the success. One thing is certain, namely with the constructionv as described there is less resistance to the flow of air bubbles from chamber33 back past the tips of propellers and into tank I2 than there is to the flow of these air bubbles through outlet port 35. The-general funnel. shape of chamber 33 in cooperation with the action. of propeller 25 parti'cularly" where the propeller is given an excess capacity over the rate of flow through restricted outlet port 35., results in this unique separation.

While the present invention has particular application to the problem of removing air from volatile fuel before delivering the same to the transfer or pumping system of an airplane it will be readily appreciated that the samehas application. wherever there exists the. equivalent problem of vapor or air inclusion in liquid to be pumped. As above pointedout it would appear that the essential requirement is the provision of a converging or funnel-like chamber the larger terminal portion of which is in communication with the fuel to be pumped, there being provided a propeller-like assembly rotatable in close proximity to the larger terminal portion of said chamber and. functioning to deliver a greater volume of liquid into the chamber than is received through the restricted outlet from the funnel-like chamber, the exces being returned to the tank past the propeller tips and carrying with it the occluded air, thus delivering the airfreed liquid through the restricted outlet to the transfer conduit.

Referring in greater detail to the preferred form of propeller shown in Figs. 1, 2, 3 and 4, an attempt will now be made to explain how this particular form accounts for superior results. The air foil section indicated generally at 26a and including a converging tip 261) is believed to account for the unusual altitude performance obtained. The blades 26 are given an optimum inclination, which is determined by the required pumping action and the factor of drag. By experiment or trial with a particular size of pump and propeller the proper inclination can be readily determined. When the proper inclination is employed a separation of the fluid occurs on the upper surface of the propeller at a point forward of the trailing edge and also at a second point on the lower surface at the trailing edge. This separation may be referred to as the burbling of flow and the position or inclination at which it occurs may be referred to as the burbling point. This separating action enters into the determination of the amount of drag, the same appearing to increase approximately a the square of the angle of inclination. If the propeller vanes or blades were of an infinite length the drag would be the result of a combination of skin friction and the eddy components set up by the accompanying conditions including pressure differences around the blade. But where the blade has a finite length as herein, there is present an additional drag resulting from pumping action or lift. There occur when pumping, an

increase of pressure on one surface of the foil section 26a and a decrease in pressure on the other. These pressures tend to equalize each other at the converging blade tip with the result that a vortex is formed as the blade moves through the liquid. Air laden fuel is caused to flow from chamber 33 radially outwardly through screen 46 while air-freed. fuel passes through restricted port 35 to the pump impeller 52 and thence to pump l6 and carburetor II. It has been found that the propeller blade construction of Figs. 4 and 4a produces materially less drag than other usable forms such as that later to be described and hence is more efficient in that less electrical energy is required to operate the motor which turns the same. It has been found that the relationship of length and surface area of the propeller is important that it is important to maintain as high a ratio as obtainable of length squared to surface area in order to keep the drag down to the minimum. The form of Figs. 4 and 4a more completely satisfy this condition than any other known form of propeller.

T While any suitable driving means maybe employed for turning propeller 25, it has been found to be particularly advantageous to connect the propeller assembly in driving relation to electrically driven booster pump 2|. This pump 2| may take a number of forms, but the electrically driven centrifugal impeller type disclosed has a number of special advantages and therefore is to be preferred. 'I'heoutlet port 35-of propeller chamber 33 forms the coaxial inlet port of pump 2|, which pump, as pointed out above and shown in Fig. 2, includes an impeller chamber Zlcenclosing a centrifugal liquid impeller 2 la effective to force the liquid out of discharge port 53 and deliver the same at n increased pressure to pump IS. The impeller 2Ia includes a plurality of radially extending vanes Zlb facing in the di-' rection of flow from restricted port 35. The inner radial portion of these vanes is exposed to the column of fuel discharged from restricted port 35, while the radial outer portion thereof lies under the outwardly flared wall 35a surrounding port 35 and in closely spaced relation thereto. The vanes 2H) and the connecting surface 2ld therebetween define with the opposed wall surface 35a guiding or directing conduits through which the fuel is centrifugally discharged radially outwardly into the scroll or volute chamber 2Ic. Impeller '2la is mounted for rotation on a shaft 54, which may also support propeller assembly 25 through the medium of an adjustable connector 56 providing for the maintenance of a definite coaxial relationship between the propeller and the booster pump impeller. Shaft 54 is driven by an electric motor 5? including a rotor 58. The usual seal and bearing arrangement indicated generally at 59 is provided between the motor and the pump impeller. A switch 6! controls the on and 011' positions of the electric motor 51, since under certain conditions it may not be desirable or necessary to operate the booster pump and vapor eliminator. Such may be the case for example when the ground temperature isrelatively low, or where flying at low altitudes below four or five thousand feet. In this connection it is important to note that propeller assembly 25 and centrifugal impeller Zia offer substantially-"no resistance to the passage thereby of fuel from the tank l2 to main engine driven pump l5 when switch BI is open and assembly I5 is not'operating.

In certain installations having less exactly requirements than that above described for an aircraft, it will be satisfactory to eliminate either the main pump [6 or the booster pump 2|, this reduction in pumping equipment being made possible by the air elimination effected by the propeller assembly.

As an example of a less expensive arrangement suitable for transferring liquid generally under conditions where air removal is important, reference is had to the alternative modification shown in Fig. 5. A small relatively inexpensive electric motor I05 drives the propeller assembly H1! located at the entrance of a straight-side funnel-shaped chamber H12. Av screen H13 prevents entry of foreign matter. The air-freed liquid may be drawn from the restricted outlet I05 through conduit I06 by a remotely located pump Ill! illustrated as being of the rotary vane or blade type and driven by any suitable means not shown. The important thing is the removal of the air by the action of the propeller cooperating with converging chamber H32, thus pre venting the liquid in the transfer line from being pulled apart by pump I01 which would be the case if the air were not previously removed.

In the arrangement of Fig. 5 there is shown a modified form of propeller assembly, which assembly while less eflicient than that of Figs. 2 and 4, nevertheless represents a very important advance. In this form, which can be readily stamped out of sheet metal, the propeller assembly Ifll is composed of four radially extending generally triangular-shaped blades I0 la, the base I lllb of each of which triangles is arcuate in shape and forms: the radially outward periphery of the blade.

,Referring to Figs-.6, r and 8, there is shown the manner in which the air is ejected and by way of example a representative set of curves bringing out to advantagethe improved performance results obtained in an actual test of an assembly such as that shown and described in Figs. 1, 2. and 4. Referring to curve i0, conditions were simulated. from zero altitude to about 12,000 feet, and as broughtout, the fuel pressure at the carburetor dropped from about 17 pounds per square inch to about 12 pounds per square inch with switch El open and booster pump 21 and Vapor eliminator 20 out of operation.. This: drop-off in pressure delivery was the result'of vapor lock, namely, so much air became included in' the fuel that the delivery of fuel was cut off. Switch El was then closed and assembly l cut into operation, whereupon the pressure at the carburetor immediately rose to slightly above 17 pounds per square inch. Fur ther reference to curve H10, brings out that as the elevation was increased to 30,000 feet and. then up to 40,000 feet, the vapor eliminator 20 continued to eject the air from the fuel entering the same notwithstanding a reduction in pressure above the liquid level and this, together with the action of booster pump 2| prevented any drop in the pressure of fuel delivery at the carburetor. As a matter of fact there was a slight rise in pres sure delivery at the carburetor between 20,000 and 35,000 feet. The remaining curves are more or less self-explanatory, curve H showing the time relationship; curve I2 showing the booster pressure in inches of mercury; curve It showing the relationship of engine speed to gallons per hour of fuel consumed; while curve I 5 shows the temperature relationship; A fill-gallon supply of 87 octane fuel having a seven pound per square inch vapor pressure was used. Figs. 6 and 7 show the actual appearance of the fuel and air bubbles in the tank in the area about the air eliminator assembly as observed through a transparent partition during the test recorded in Fig. 8, and at altitudes respectively of 30,000 feet and 40,000 feet. The air bubbles can be seen very clearly and are indicated in the figures in dotted lines.

As a further feature of particular importance, advantage may be taken of the action of assembly l5 for supercharging the tank I2. This is of particular importance on sustained flight where if the tank were muted to atmosphere the loss of fuel would in some cases run as high as 7 to 10 per cent. at altitudes of the order of 30,000 feet. Where the tank is thus to be supercharged, there will of course be employed a suitable relief valve assembly indicated schematically at Ma such as that disclosed in co-pending Roth et a1. Patent No. 2,345,547, issued March 28, 1944, the function of which is to limit both the maximum value of pressure in the tankas well as the degree of vacuum.

As a final check on the improved results attributable to the propeller 25, the same was removed and curve 10:: shown in dotted lines was plotted, from which it is readily apparent that the booster pump 2| alone will not maintain the delivery pressure at the inlet of main fuel pump I 8. Not only is this true, but it will be seen further from an examination of curve H01: that it was not feasible to attempt to simulate altitude above about 30,000 feet. In other Words, due to the occlusion of air bubbles in the fuel entering the booster pump 2|, without. the use of the va- 8 por eliminating propeller 2.5, vapor lock occurred at about 30,000 feet which, in. actual fiight, would result in a loss of altitude due to failure to maintain the necessary delivery pressure at the carburetor. No attempt has. been made to incorporate the other curves corresponding to lilw, since to do somight unduly confuse the picture.

While I have disclosed and described my invention in connection with certain specific embodiments thereof, this-is to be understood as being by way of example only, and that my invention is to be defined by the appended claims.

I claim: I

1. In an arrangement'for transferring a liquid from a source of liquid supply to a point remote therefrom wherein air is unavoidably included in said liquid to be transferred, said arrangement including means in communication with said liquid supply for receiving a portion thereof to be transferred to said remote point, said means comprising a housing having a general funnelshaped chamber therein, said, chamber being defined in part by a first relatively large terminal port, a surrounding converging. wall terminating in a second restricted terminal port having a substantially smaller diameter than that of said first terminal port, a propeller blade-like assembly including a plurality of radially extending blades having an overall diameter substantially greater than the diameter of said second terminal port and positioned for coaxial rotation with the tips of said blades in generally coplanar relation to said first terminal port of said chamber, and means for moving liquid from said second restricted port to said. remote point including a cond-uit and a pump having a rotary impeller for displacing said liquid in the direction of saidremote point, and means for rotating said pump and said propeller, said propeller having a fluid displacing capacity greater than that of said pump whereby an excess. of liquid is moved into said funnel-shaped chamber over that received by said pump, said excess being ejected back past the tips of said propeller and into the main body of said liquid supply, said excess returned fuel removing therewiththe excess air contained in the liquid introduced into said chamber whereby air-freed liquid is delivered to said pump for transmission to said remote point.

2. In an arrangementfor transferring a liquid from a source of liquid supply to a point remote therefrom under conditions-wherein occluded air is unavoidably precipitated in the liquid to be transferred, said arrangement including means in communication with said liquid supply for receiving a portion thereof to be transferred, said receiving means comprising an ejector housing formed with a bore therethrough, said bore being defined in part by a first terminal port, a surrounding inner peripheral wall converging in the direction of the other extremity of said bore and terminating in a restricted outlet port, said surrounding inner peripheral Wall being generally concave in shape, a propeller blade assembly including a plurality of radially extending blades having an overall diameter substantially greater than the diameter of said restricted outlet port, said propeller blade assembly being positioned in generally coplanar relation to said first terminal port of said bore for coaxial rotation with reference thereto, a generally annular shaped ring spaced from said propeller assembly and having a bore therethrough defined by a generally convex inner peripheral wall terminating in an outlet-port having a diameter less than the overall diameter of said propeller assembly and functioning to direct liquid fiow to said propeller assembly, said ring being further defined by a diverging underside portion, means defining a pump including a housing, said housing formed with an open-ended impeller chamber, said ejector housing being fastened in the open end of said chamber, said restricted outlet port of said ejector housing defining a coaxial inlet port to said pump chamber, a centrifugal pump impeller received in said pump chamber and conduit means connecting said propeller assembly and said pump impeller together for rotation about the same axis and an electric motor for driving said impeller and propeller assembly, said propeller assembly having a displacement greater than that of said pump impeller whereby a greater volume of liquid is delivered into said ejector chamber than is received by said pump impeller with the result that an excess of liquid is ejected back past said propeller tips into the main body of liquid supply, said excess returned liquid carrying with it the occluded air thus delivering air-freed liquid to said pump impeller for transmission to said remote point.

3. In an arrangement for transferring a liquid from a source of liquid supply to a point remote therefrom wherein air is unavoidably included in said liquid to be transferred, said arrangement including means in communication with said liquid supply for receiving a portion thereof to be transferred to said remote point, said means comprising a housing having a general funnelshaped chamber therein, said chamber being defined in part by a first relatively large terminal port, a surrounding converging wall terminating in a second restricted terminal port having a substantially smaller diameter than that of said first terminal port, a propeller blade assembly including a pair of radially oppositely extending blades each being characterized by converging tip portions, said propeller having an overall diameter substantially greater than the diameter of said second terminal port and positioned for coaxial rotation with the tips of said blades in generally coplanar relation to said first terminal port of said chamber, and means for moving liquid from said second restricted port to said remote point including a conduit and a pump having a rotary impeller for displacing said liquid in the direction of said remote point, and

means for rotating said pump and said propeller, said propeller having a fluid displacing capacity greater than that of said pump whereby an excess of liquid is moved into said funnel-shaped chamber over that received by said pump, said excess being ejected back past the tips of said propeller and into the main body of said liquid supply, said excess returned fuel removing therewith the excess air contained in the liquid introduced into said chamber whereby air-freed liquid is delivered to said pump for transmission to said remote point.

4. In an arrangement for transferring a liquid from a source of liquid supply to a point remote therefrom under conditions wherein occluded air is unavoidably precipitated in the liquid to be transferred, said arrangement including means in communication with said liquid supply for receiving a portion thereof to be transferred, said receiving means comprising an ejector housing formed with a bore therethrough, said bore being defined in part by a first terminal port, a surrounding inner peripheral wall converging in the direction of the other extremity 10 of said bore and terminating in a restricted outlet port, said surrounding inner peripheral Wall being generally concave in shape, a propeller blade assembly including a single pair of radially oppositely extending blades having a generally elongated cross-section throughout the radial extent thereof except for the terminal portion, said terminal portion converging in points at the tips of said blades, said propeller having an overall diameter substantially greater than the diameter of said restricted outlet port, said propeller blade assembly being positioned in generally coplanar relation-to said first terminal port of said bore for coaxial rotation with reference thereto, a generally annular shaped ring spaced from said propeller assembly and having a bore therethrough defined by a generally convex inner peripheral wall terminating in an outlet port having a diameter less than the overall diameter of said propeller assembly and functioning to direct liquid flow to said propeller assembly, said ring being further defined by a diverging underside portion, means defining a pump including a housing, said housing formed with an open-ended impeller chamber, said ejector housing being fastened in the open end of said chamber, said restricted outlet port of said ejector housing defining a coaxial inlet port to said pump chamber, a centrifugal pump impeller received'in said pump chamber and conduit means connecting said propeller assembly and said pump impeller together for rotation about the same axis and an electric motor for driving said impeller and propeller assembly, said propeller assembly having a displacement greater than that of said pump impeller whereby a greater volume of liquid is delivered into said ejector chamber than is received by said pump impeller with the result that an excess of liquid is ejected back past said propeller tips into the main body of liquid supply, said excess returned liquid carrying with it the occluded air thus delivering air-freed liquid to said pump impeller for transmission to said remote point.

5. In an aircraft volatile fuel conditioning and transferring arrangement for moving said fuel from a remotely located fuel supply tank to the aircraft carburetor, including an electrically driven selectively operable centrifugal booster pump located adjacent said fuel tank, the combination therewith of means in communication with the fuel in said tank for receiving a por tion thereof ejecting therefrom the air included therein and delivering the .air freed fuel to said centrifugal booster pump, said means comprising a housing formed with a coaxial bore there-- through defined in part by first relatively large terminal port joined by generally funnel shaped converging surrounding wall portion with a restricted terminal outlet port, said restricted outlet port also forming the inlet port of said centrifugal booster pump, a propeller assembly including at least one pair of radially oppositely extending blades having an overall diameter substantially greater than the diameter of said outlet port, said propeller assembly being positioned in generally coplanar relation to said relatively large terminal port, means connecting said propeller assembly to .said centrifugal impeller for rotation therewith about the same axis, and motive means for rotating said impeller and propeller, said propeller having a pumping capacity greater than that of said booster pump impeller whereby an excess of fuel is umped into said converging chamber over and above that 11 which is received by said centrifugal impeller, said excess fuel being ejected back past the tips of said'propeller and into the main body of fuel in said tank, the ejection of said excess fuel being eifeotive to remove therewith the critical portion of the air incorporated in the fuel delivered into said converging chamber by said propeller, whereby to deliver air freed fuel to said rotary impeller, said arrangement being further particularly characterized by the fact that said removed air returned to said tank becomes effective to increase the pressure in the area above thefuel in said tank to thus supercharge said tank, and means including a relief valve assembly for controlling the degree of said supercharged pressure.

6. In a pump construction including a pump casing formed with an inlet throat, an impeller with pumping vanes und-erlapping said throat, an agitating propeller positioned to act on material fed to said throat before the same reaches said vanes, said throat being funnel-like in shape 1 and defined by a generally concave inner peripheral Wall leading from a relatively large outer inlet terminal to a converged outlet terminal adjacent said impeller vanes, a guide shield mounted in advance of the throat and the agitating propeller defining an annular bell mouthed passage to the throat in localized transverse communication with the exterior of said shield, said shield including an outlet terminal opening 5 by said propeller radiallyoutwardly between the enlarged terminal of said throat and the exterior of said guide shield.

. v LOUIS 'G. BURNS.

1 n REFERENCES CITED The following references are of record in the file "of this patent: v

UNITED STATES PATENTS Number Name Date 1,623,074 Tartrais Apr. 5, 19-27 2,151,043 Paton 1 Mar. 21;, 1937 2,157,737 -Janssen 1 1 .May 9., 1939 2,209,856 Smith et a1. a -July 30, 1940 20 2,238,502 Muir e't al. 1 Apr. 15, 1941 2,292,993 Curtis Aug. 11-, 1942 2,306,297 Curtis Dec. 22,1942 2,306,298 Curtis Dec. 22, 1942 2,306,299 Curtis -2 Dec. 22, 1-942 35 2,345,547 Roth et a1. Mar..28, 1944 FOREIGN PATENTS Number Country Date 30 288,642 Great Britain sure Mar. 7,

12 adjacent said propeller ofiesser diameter; than the overall diameter of .said prdp'eller whereby to direct air-laden fuel. generally centrally of said propeller and to provide :a. .path for air ejected

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